1. Field of the Invention
The present invention generally relates to a method of redistributing driving torque based on one or more load conditions in a 4-wheel drive (4WD) vehicle. More particularly, it relates to a method of redistributing driving torque among all wheels (e.g., between the front and rear wheels) of a 4WD vehicle based on one or more load conditions that can cause significant damage or wear and tear to driveline components such as CV joints and driveshaft.
2. Description of the Related Art
In 4WD vehicles, various systems are known for distributing driving torque between front and rear wheels. For instance, driving torque can be distributed by employing a limited slip center or inter-axle differential, or by employing a clutch of a hydraulic or electromagnetic type in a torque path for varying the driving torque transmitted there through. The above known driving torque redistribution systems can be used to, e.g., enhance the turning performance of 4WD vehicles. In particular, the driving torque is distributed or transferred based on a difference of speed between the front and rear wheels, engine output when the vehicle speed is less than a given value, or line pressure in a transfer clutch.
Furthermore, most 4WD vehicles are designed so that one pair of wheels (front or rear) is the primary driving wheels and the other pair is the auxiliary driving wheels. In other words, under normal driving conditions, the primary driving wheels receive most of the torque and the auxiliary driving wheels receive a smaller amount of torque (or none at all). In some 4WD vehicles, the primary driving wheels are the front wheels, and in other 4WD vehicles the primary driving wheels are the rear wheels.
When a 4WD vehicle encounters a high load condition caused by climbing a steep hill, towing a trailer, or other heavy load condition, the 4WD vehicle typically requires a large amount of driving torque in its driveline system to cope with the heavy load. Such heavy application of the driving torque to the driveline system inevitably causes wear and tear or even significant damage to various components of the driveline system.
None of the above known driving torque redistribution systems is able to distribute or transfer torque between front and rear wheels based on high load conditions. Accordingly, the above known driving torque redistribution systems cannot prevent wear and tear and damage of the components of the driveline systems when 4WD vehicles encounter one or more high load conditions.
Accordingly, the present invention is provided in order to increase the life cycle of driveline components by redistributing torque among different wheels in a 4WD vehicle based on one or more high load conditions. For example, in a 4WD vehicle where most (or all) of the driving toque is normally transmitted through the front wheels, when the vehicle encounters a high load condition, a great deal of wear and tear, or even damage, may occur to the drive train components of the front wheels. However, when such a high load condition is sensed, the instant invention transfers an additional amount of torque through the rear wheels, in order to reduce wear and tear or damage to the drive train of the front wheels. Of course, the instant invention also applies to a system where most of the driving torque is normally transmitted through the rear wheels.
Various methods are provided in the torque redistribution method of the present invention that would reduce the torque and the subsequent damage of certain components of the driveline system by controlling torque redistribution among different wheels of the vehicle based on one or more high load conditions on the components of the driveline system.
The load-based torque redistribution system of the instant invention ensures that the excessive torque due to the high load on the front or rear wheels, the primary driving wheels of a 4WD vehicle, is appropriately transferred or distributed to the auxiliary driving wheels so as to alleviate the load and reduce wear and tear.
In accordance with the present invention, a method of redistributing driving torque between front and rear driving wheels of a vehicle, when the front of a rear wheels are traveling at essentially the same speed, includes: determining a vehicle condition corresponding to load, based upon at least one vehicle parameter; comparing the determined vehicle condition to a predetermined value, wherein if the determining vehicle condition exceeds the predetermined value, a high load condition exists; and redistributing the driving torque between the front and rear wheels, when the determining step determines that a high load condition exists.
Additionally, a system for redistributing driving torque distributed between front and rear wheels of a vehicle, when the front and rear wheels are traveling at essentially the same speed, includes: a front driveline for driving the front wheels; a rear driveline for driving the rear wheels; a torque transfer unit connecting the front and rear drivelines for distributing torque, from a power source, between the front and rear drivelines; at least one vehicle sensor; and a controller, coupled to the sensor and the differential, for controlling torque split of the differential in response to the sensor.